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venerdì 28 gennaio 2011

The seismic vibrations of the stars can reveal valuable information about their age, size and internal dynamics.The Kepler telescope from NASA, dedicated specifically to search for extrasolar planets, is only entered as 100,000.

In English we call them "starquake, earthquakes star (or perhaps it would be more correct to call them" stellemoti?).Are vibrations that shake the surface of the star, whose analysis you can discover a lot about the star itself: how many years and than he still has, its structure, as it is, forming storms and starspots.Just as earthquakes on Earth, as it is revealing the internal structure of our planet, so the way in which the stars of their range is a spy hidden features.

This concept, which in itself does not have anything particularly original, now has the chance to be put to work on a large scale by NASA's Kepler mission.The program Kepler Asteroseismic Investigation aims to monitor the vibration surface of thousands of stars to find out more about them.

Although its primary mission remains to hunt down the extrasolar planets similar to Earth, the technical capabilities of the space telescope allow to obtain, as they say, two birds with one stone.In fact, the mechanism by which Kepler identifies exoplanets is the same that can detect the stellar vibrations.Thanks all'avanzatissima technology captures the subtle variations in brightness of a star when a planet (a microbe to the comparison) in front of the orbit.Even the seismic oscillations affecting the area of the disk, resulting in considerable changes in the brightness of the star.So Kepler has been collecting secret information about 100,000 stars.

The seismic waves in the stars are the result of turbulent convection inside.When the waves hit the surface, it begins to vibrate like a bell.Since the speed of wave propagation depends on its internal structure, that's what scientists can deduce there is still hydrogen in the star (it is the fuel for thermonuclear fusion reactions), estimating how long it shines and how long it will go ahead before disappearing.A celestial dating useful to refine models of stellar evolution.And most of all to get to know the galactic neighbors.

Little green object is WISEPC J045853.90+643451.9 , first brown dwarf discovery by WISE NASA Space Infrared Telescope. This object is placed between 18 and 30 light year from Earth, and it's the coolest body known with only 326°C. Credit: NASA

University of Hertfordshire astronomers have measured the distances to 11 of the coolest objects ever discovered outside our solar system. The 11 cool objects – known as brown dwarfs – have masses intermediate between stars (more massive) and planets (less massive), and as a result do not burn hydrogen, making them extremely cool.

The work led by Federico Marocco, an astrophysicist in UH’s Centre for Astrophysics Research was carried out as part of a collaboration between UH, the astronomical Observatory of Torino and a wider international group.

Astronomers call very cool brown dwarfs like the ones discovered ‘T dwarfs’ and Federico and his team have discovered many of the coolest known examples ever found.

Federico Marocco said: “A proper understanding of such cool atmospheres is important for interpreting warm giant planets as well as brown dwarfs, since planet temperatures can overlap with those of brown dwarfs”.

The team made deep infrared measurements of each T dwarf with the UK Infrared telescope over a 4 year period and this allowed them to determine the distances of each dwarf. It was revealed the dwarfs were between 30 and 300 light years from the Sun. The new distance measurements show that our understanding of cool atmospheres is incomplete, and establishes benchmark measurements that future theories will be tested against.

“It may be that our solar system’s nearest neighbor is an undiscovered brown dwarf, just waiting to be revealed” said Marocco. The new discoveries have been published in a paper in the academic journal Astronomy & Astrophysics.

A massive star flung away from its former companion is plowing through space dust. The result is a brilliant bow shock, seen as a yellow arc in a new image from NASA's Wide-field Infrared Survey Explorer, or WISE.

The star, named Zeta Ophiuchi, is huge, with a mass of about 20 times that of our sun. In this image, in which infrared light has been translated into visible colors we see with our eyes, the star appears as the blue dot inside the bow shock.

Zeta Ophiuchi once orbited around an even heftier star. But when that star exploded in a supernova, Zeta Ophiuchi shot away like a bullet. It's traveling at a whopping 54,000 miles per hour (or 24 kilometers per second), and heading toward the upper left area of the picture.

As the star tears through space, its powerful winds push gas and dust out of its way and into what is called a bow shock. The material in the bow shock is so compressed that it glows with infrared light that WISE can see. The effect is similar to what happens when a boat speeds through water, pushing a wave in front of it.

This bow shock is completely hidden in visible light. Infrared images like this one from WISE are therefore important for shedding new light on the region.

giovedì 27 gennaio 2011

This image of the Hubble Ultra-Deep Field is a small part of the deepest infrared image ever taken of the universe. The small blue box outlines the area where astronomers found what may be the most distant galaxy ever seen, 13.2 billion light-years away, meaning its light was emitted just 480 million years after the Big Bang. It is small and very faint and is shown separately in the larger box. The galaxy is shown as blue because it emitted very blue light due to its high rate of star birth, although by the time the light reached Hubble it had been stretched into the infrared by the expansion of space, giving it a redshift value of about 10. Its official name is UDFj-39546284, but astronomers refer to it as the "redshift 10 galaxy candidate." (Credit: NASA, ESA, Garth Illingworth (University of California, Santa Cruz) and Rychard Bouwens (University of California, Santa Cruz and Leiden University) and the HUDF09 Team)

Astronomers have pushed NASA's Hubble Space Telescope to it limits by finding what they believe to be the most distant object ever seen in the universe -- at a distance of 13.2 billion light years, some 3% of the age of universe. This places the object roughly 150 million light years more distant than the previous record holder. The observations provide the best insights yet into the birth of the first stars and galaxies and the evolution of the universe.

The research is published Jan. 27, 2011, in the journal Nature.

The dim object is a compact galaxy made of blue stars that existed only 480 million years after the Big Bang. It is tiny. Over one hundred such mini galaxies would be needed to make up our Milky Way.

Co-author Ivo Labbé of the Carnegie Observatories puts the findings into context: "We are thrilled to have discovered this galaxy, but we're equally surprised to have found only one. This tells us that the universe was changing very rapidly in early times."

Previous searches had found 47 galaxies at somewhat later times, when the universe was about 650 million years old. The rate of star birth therefore increased by about ten times in the interval from 480 million years to 650 million years. "This is an astonishing increase in such a short period, happening in just 1% of the age of the universe," says Labbé.

"These observations provide us with our best insights yet into the earliest primeval objects yet to be found," adds Rychard Bouwens of the University of Leiden in the Netherlands.

Astronomers don't know exactly when the first stars appeared in the universe, but every step back in time takes them deeper into the early universe's "formative years" when stars and galaxies were just beginning to emerge in the aftermath of the Big Bang.

"We're moving into a regime where there are big changes afoot. And what it tells us is that if we go back another couple hundred million years toward the Big Bang we'll see absolutely dramatic things happening. That will be the time where the first galaxies really are starting to get built up," says Garth Illingworth of the University of California at Santa Cruz.

The even more distant proto galaxies will require the infrared vision of NASA's James Webb Space Telescope, which is the successor to Hubble, and next-generation ground-based telescopes, such as the Giant Magellan Telescope. These new facilities, planned for later this decade, will provide confirming spectroscopic measurements of the tremendous distance of the object being reported.

After over a year of detailed analysis, the galaxy was positively identified in the Hubble Ultra Deep Field -- Infrared (HUDF-IR) data taken in the late summer of both 2009 and 2010. These observations were made with the Wide Field Planetary Camera 3 (WFPC3) starting just a few months after it was installed into the Hubble Space Telescope in May of 2009, during the last NASA space shuttle servicing mission to Hubble.

The object appears as a faint dot of starlight in the Hubble exposures. It is too young and too small to have the familiar spiral shape that is characteristic of galaxies in the local universe, such as the Milky Way. Though individual stars can't be resolved by Hubble, the evidence suggests that this is a compact galaxy of hot stars that first started to form over 100 to 200 million years earlier in a pocket of dark matter.

The proto galaxy is only visible at the farthest infrared wavelengths observable by Hubble. This means that the expansion of the universe has stretched its light farther that any other galaxy previously identified in the HUDF-IR, to the very limit of Hubble's capabilities.

Astronomers plumb the depths of the universe by measuring how much the light from an object has been stretched by the expansion of space. This is called redshift value or "z." Before Hubble was launched, astronomers could only see galaxies out to a z approximately 1, corresponding to 6 billion years after the Big Bang. The Hubble Deep Field taken in 1995 leapfrogged to z=4, or roughly 90 percent of the way back to the beginning of time. The new Advanced Camera and the Hubble Ultra Deep Field pushed back the limit to z~6 after the 2002 servicing mission. Hubble's first infrared camera, the Near Infrared Camera and Multi Object Spectrometer reached out to z=7. The WFC3/IR reached back to z~8, and now plausibly has penetrated for the first time to z=10 (about 500 million years after the Big Bang). The Webb Space Telescope is expected to leapfrog to z~15, and possibly beyond. The very first stars may have formed between z of 30 to 15, or 100 to 250 million years post Big Bang.

The hypothesized hierarchical growth of galaxies -- from stellar clumps to majestic spirals -- didn't become evident until the Hubble Space Telescope deep field exposures. The first 500 million years of the universe's existence, from a z of 1000 to 10 is now the missing chapter in the hierarchical growth of galaxies. It's not clear how the universe assembled structure out of a darkening, cooling fireball of the Big Bang. As with a developing embryo, astronomers know there must have been an early period of rapid changes that would set the initial conditions to make the universe of galaxies that exist today. Astronomers eagerly await the new space and ground-based telescopes to find out!

mercoledì 26 gennaio 2011

Betelgeuse, the red supergiant star at 640 light years from here, is dying.Massimo Turatto, director OA Trieste, in this interview reveals what really happens when it came his time (within the next million years), what you see from Earth because it would be better not to look out the window.

One morning we wake up and, looking out the window, we will see two suns shining above the city. Not exactly the two disks, as in Star Wars, but another new source beam in the sky, though point. Science fiction? No. It is the scenario that probably will occur (and will last for a few months) when the red supergiant Betelgeuse, now dying, will end his day, disintegrating in catastrophic explosions, visible to the naked eye, given its proximity to us, is only 640 light years from here, in the constellation of Orion.

It was enough that the physical Brad Carter, University of Queensland, to declare the site news.com.au that the event can happen before the infamous 2012, or at any time in the next few million years, to unleash the Apocalypse Cassandre , terrorizing the followers of the Mayan prophecy, galvanize fans of the famous saga of George Lucas, excited at the thought of Earth as the world Tatooine.

Sorry to play the part of the damper. But there is little to fear, and perhaps even less to celebrate. Massimo
Turatto, Director of INAF - Italian Astronomic Observatory of Trieste in this interview reveals truths and lies on the supernova that "soon" explode. Read it slowly, so it is useless to rush away from home. Nobody knows when the show will be staged, but it is very unlikely to happen right now. Also, it might not be so convenient to stay in the front row watching. We are still talking about a mega-bomb that explodes in our galaxy.

Massimo Turatto, it is possible that Betelgeuse explodes before 2012?
There is absolutely no way to predict it. What we know for sure is that stars of this type, at the end of their evolution, self-destruct in a spectacular explosion. Almost all the material is ejected into interstellar space at a speed of 30,000 kilometers per second, is released an impressive amount of energy and for a few days ago more light supernova in the galaxy. In the end, only leaves "ashes" means a compact neutron star or a black hole. Betelgeuse is intended to make this end soon enough: it is a red supergiant, 20 times larger than the Sun, now in the terminal phase. Means that it can die tomorrow or millions of years in cosmological terms, it is still a fraction of a very short time.

How to recognize a star "dying"?
The temperature of the outer layers of Betelgeuse is about 3,500 ° C, much lower than a young star of its size. At this stage, you are running low on fuel that powers the thermonuclear reactions in the core, a true central star, where the heat can reach tens of millions of degrees.

What you would see from Earth, following a nuclear disaster like that?
If Betelgeuse burst when it is angularly close to the Sun, it would be so brilliant that we would see as a bright dot in the sky, even during the day, but imagine a fireball, like the Sun! It would however be a 'point-like image, but very bright point.

It's never happened to see a supernova up close?
There are historical evidence of similar events in past centuries and millennia, like the explosion of a supernova in 1054, in the constellation of the Crab. In 1572 the Danish astronomer Tycho Brahe, he remarked, in 1604 Johannes Kepler and Galileo Galilei I saw another naked eye, in the Milky Way. The last, occurring without the aid of telescopes, dates back to 1987, was in the Large Magellanic Cloud, satellite galaxy to our own. Paradoxically, it is more difficult to detect such objects in our galaxy, because the clouds of dust and gas in the galactic plane obscures the view.

How frequent are the explosions of supernovae?
The space and ground telescopes can detect dozens every day across the observable Universe. In the Milky Way it has on average one every 50 years. It must be said that Betelgeuse is not the only candidate for an imminent explosion. There are dozens of massive stars and older, fairly close to us and at the same level.

There would be consequences for us?

I would have some concern, at least in the early hours. In addition to visible light, harmless, we would be hit by a stream of invisible electromagnetic radiation, particularly X-rays and ultraviolet rays, which could potentially change the Earth's atmosphere, ionization, and lowering it. From Betelgeuse we'll get a lot of energy of this kind between 5,000 and 10,000 times higher than the Sun, but being protected by the atmosphere, it is difficult to make a quantitative estimate of the impact on health and the environment. Almost certainly, such an event would send tilt in satellite telecommunications and may burn room sensors mounted on space telescopes, not rated for such intense radiation.

A supernova could change the balance of the planet?

The distance at which there is no Betelgeuse. However, in the early hours there would be risks. It is not impossible, in general, that a supernova close to the Earth can cause serious damage. According to some, is one of the hypotheses to explain the mass extinction of dinosaurs.

What the scientists could discover in such an occasion?

Very much. The observations of 1987 have allowed us to confirm that the explosion of massive stars by gravitational collapse occurs and revealed 20 neutrinos, particles that constantly rain down on Earth but do not allow themselves to grasp. For astronomers would be great opportunity to closely observe a phenomenon that may give rise to drops blacks.

The Sun is destined to end?

No, primarily concerned with the fate of supernova stars with masses greater than 8 solar masses. But the Sun conceals other mysteries. For example I am fascinated by the idea that has maintained its radiation fairly constant for billions of years to allow the development of life and intelligent life.

The Sloan Digital Sky Survey-III (SDSS-III) has released the largest digital color image of the sky ever made, and its free to all. The image has been put together over the last decade from millions of 2.8-megapixel images, thus creating a color image of more than a trillion pixels. This terapixel image is so big and detailed that one would need 500,000 high-definition TVs to view it at its full resolution.

"This image provides opportunities for many new scientific discoveries in the years to come," exclaims Bob Nichol, a professor at the University of Portsmouth and Scientific Spokesperson for the SDSS-III collaboration.
The new image is at the heart of new data being released by the SDSS-III collaboration at 217th American Astronomical Society meeting in Seattle. This new SDSS-III data release, along with the previous data releases that it builds upon, gives astronomers the most comprehensive view of the night sky ever made. SDSS data have already been used to discover nearly half a billion astronomical objects, including asteroids, stars, galaxies and distant quasars. The latest, most precise positions, colors and shapes for all these objects are also being released.
"This is one of the biggest bounties in the history of science," says Professor Mike Blanton from New York University, who is leading the data archive work in SDSS-III. Illustration: This illustration shows the wealth of information on scales both small and large available in the SDSS-III's new image. The picture in the top left shows the SDSS-III view of a small part of the sky, centered on the galaxy Messier 33 (M33). The middle top picture is a further zoom-in on M33, showing the spiral arms of this Galaxy, including the blue knots of intense star formation known as "HII regions." The top right-hand picture is a further zoom into M33 showing the object NGC604, which is one of the largest HII regions in that galaxy. The figure at the bottom is a map of the whole sky derived from the SDSS-III image, divided into the northern and southern hemispheres of our galaxy. Visible in the map are the clusters and walls of galaxies that are the largest structures in the entire universe. (Credit: M. Blanton and the SDSS-III)

Blanton and many other scientists have been working for months preparing the release of all this data. This data will be a legacy for the ages, explains Blanton, as previous ambitious sky surveys like the Palomar Sky Survey of the 1950s are still being used today. We expect the SDSS data to have that sort of shelf life," comments Blanton.

The image was started in 1998 using what was then the worlds largest digital camera a 138-megapixel imaging detector on the back of a dedicated 2.5-meter telescope at the Apache Point Observatory in New Mexico, USA. Over the last decade, the Sloan Digital Sky Survey has scanned a third of the whole sky. Now, this imaging camera is being retired, and will be part of the permanent collection at the Smithsonian in recognition of its contributions to Astronomy.
"Its been wonderful to see the science results that have come from this camera," says Connie Rockosi, an astronomer from the University of California Santa Cruz, who started working on the camera in the 1990s as an undergraduate student with Jim Gunn, Professor of Astronomy at Princeton University and SDSS-I/II Project Scientist. Rockosi's entire career so far has paralleled the history of the SDSS camera. "Its a bittersweet feeling to see this camera retired, because Ive been working with it for nearly 20 years," she says.
But what next? This enormous image has formed the basis for new surveys of the Universe using the SDSS telescope.

These surveys rely on spectra, an astronomical technique that uses instruments to spread the light from a star or galaxy into its component wavelengths. Spectra can be used to find the distances to distant galaxies, and the properties (such as temperature and chemical composition) of different types of stars and galaxies.
"We have upgraded the existing SDSS instruments, and we are using them to measure distances to over a million galaxies detected in this image," explains David Schlegel, an astronomer from Lawrence Berkeley National Laboratory, and the Principal Investigator of the new SDSS-III Baryon Oscillation

Spectroscopic Survey (BOSS). Schlegel explains that measuring distances to galaxies is more time- consuming than simply taking their pictures, but in return, it provides a detailed three-dimensional map of the galaxies' distribution in space.
BOSS started taking data in 2009 and will continue until 2014, explains Schlegel. Once finished, BOSS will be the largest 3-D map of galaxies ever made, extending the original SDSS galaxy survey to a much larger volume of the Universe. The goal of BOSS is to precisely measure how so-called "Dark Energy" has changed over the recent history of the Universe. These measurements will help astronomers understand the nature of this mysterious substance. "Dark energy is the biggest conundrum facing science today," says Schlegel, "and the SDSS continues to lead the way in trying to figure out what the heck it is!"

In addition to BOSS, the SDSS-III collaboration has been studying the properties and motions of hundreds of thousands of stars in the outer parts of our Milky Way Galaxy. The survey, known as the Sloan Extension for Galactic Understanding and Exploration or SEGUE started several years ago but has now been completed as part of the first year of SDSS-III.

In conjunction with the new image, astronomers from SEGUE are also releasing the largest map of the outer Galaxy ever released. "This map has been used to study the distribution of stars in our Galaxy," says Rockosi, the Principal Investigator of SEGUE. "We have found many streams of stars that originally belonged to other galaxies that were torn apart by the gravity of our Milky Way. We've long thought that galaxies evolve by merging with others; the SEGUE observations confirm this basic picture."

SDSS-III is also undertaking two other surveys of our Galaxy through 2014. The first, called MARVELS, will use a new instrument to repeatedly measure spectra for approximately 8500 nearby stars like our own Sun, looking for the tell-tale wobbles caused by large Jupiter-like planets orbiting them. MARVELS is predicted to discover around a hundred new giant planets, as well as potentially finding a similar number of "brown dwarfs" that are intermediate between the most massive planets and the smallest stars.
The second survey is the APO Galactic Evolution Experiment (APOGEE), which is using one of the largest infrared spectrographs ever built to undertake the first systematic study of stars in all parts of our Galaxy; even stars on the other side of our Galaxy beyond the central bulge. Such stars are traditionally difficult to study as their visible light is obscured by large amounts of dust in the disk of our Galaxy. However, by working at longer, infrared wavelengths, APOGEE can study them in great detail, thus revealing their properties and motions to explore how the different components of our Galaxy were put together.
"The SDSS-III is an amazingly diverse project built on the legacy of the original SDSS and SDSS-II surveys," summarizes Nichol. "This image is the culmination of decades of work by hundreds of people, and has already produced many incredible discoveries. Astronomy has a rich tradition of making all such data freely available to the public, and we hope everyone will enjoy it as much as we have."

domenica 23 gennaio 2011

Phobos, as seen by Mars Express on Jan. 9, 2011 from a distance of about 100 km. Credit: ESA/DLR/FU Berlin (G. Neukum

The Mars Express team released the images today from the close flyby the spacecraft made of Phobos on January 9. The images weren’t downloaded from Mars Express until Jan. 18, and then they were processed, so these are hot off the press. The team didn’t provide much explanation, but enjoy the images. There’s one 3-D view in the group, so grab your 3-D glasses.

Here’s the on 3-D view, and the team explained that due to the stereo viewing geometry during the flyby a small part of the moon’s edge is only visible for the right eye resulting in odd 3D-perception in this area. This part has been slightly adjusted for better viewing. Also, for the left eye at the left edge of the image four small data gaps have been interpolated.

NASA's Mars Exploration Rover Opportunity is spending the seventh anniversary of its landing on Mars investigating a crater called "Santa Maria," which has a diameter about the length of a football field. Image credit: NASA/JPL-Caltech/Cornell/ASU

PASADENA, Calif. - The team operating NASA's Mars rover Opportunity will temporarily suspend commanding for 16 days after the rover's seventh anniversary next week, but the rover will stay busy.

For the fourth time since Opportunity landed on Mars on Jan. 25, 2004, Universal Time (Jan. 24, Pacific Time), the planets' orbits will put Mars almost directly behind the sun from Earth's perspective.

During the days surrounding such an alignment, called a solar conjunction, the sun can disrupt radio transmissions between Earth and Mars. To avoid the chance of a command being corrupted by the sun and harming a spacecraft, NASA temporarily refrains from sending commands from Earth to Mars spacecraft in orbit and on the surface. This year, the commanding moratorium will be Jan. 27 to Feb. 11 for Opportunity, with similar periods for the Mars Reconnaissance Orbiter and Mars Odyssey orbiter.

Downlinks from Mars spacecraft will continue during the conjunction period, though at a much reduced rate. Mars-to-Earth communication does not present risk to spacecraft safety, even if transmissions are corrupted by the sun.

NASA's Mars Reconnaissance Orbiter will scale back its observations of Mars during the conjunction period due to reduced capability to download data to Earth and a limit on how much can be stored onboard.

Opportunity will continue sending data daily to the Odyssey orbiter for relay to Earth. "Overall, we expect to receive a smaller volume of daily data from Opportunity and none at all during the deepest four days of conjunction," said Alfonso Herrera, a rover mission manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

The view is presented in false color to emphasize differences among materials in the rocks and the soils. Image credit: NASA/JPL-Caltech/Cornell/ASU

The rover team has developed a set of commands to be sent to Opportunity in advance so that the rover can continue science activities during the command moratorium.

"The goal is to characterize the materials in an area that shows up with a mineralogical signal, as seen from orbit, that's different from anywhere else Opportunity has been," said JPL's Bruce Banerdt, project scientist for Opportunity and its rover twin, Spirit. The area is at the southeastern edge of a crater called "Santa Maria," which Opportunity approached from the west last month.

Drives last week brought Opportunity to the position where it will spend the conjunction period. From that position, the rover's robotic arm can reach an outcrop target called "Luis de Torres." The rover's Moessbauer spectrometer will be placed onto the target for several days during the conjunction to assess the types of minerals present. The instrument uses a small amount of radioactive cobalt-57 to elicit information from the target. With a half-life of less than a year, the cobalt has substantially depleted during Opportunity's seven years on Mars, so readings lasting several days are necessary now to be equivalent to much shorter readings when the mission was newer.

The panorama spans 125 compass degrees, from north-northwest on the left to south-southwest on the right. Image credit: NASA/JPL-Caltech/Cornell/ASU

Opportunity will also make atmospheric measurements during the conjunction period. After conjunction, it will spend several more days investigating Santa Maria crater before resuming a long-term trek toward Endurance crater, which is about 22 kilometers (14 miles) in diameter and, at its closest edge, about 6 kilometers (4 miles) from Santa Maria.

Opportunity's drives to the southeastern edge of Santa Maria brought the total distance driven by the rover during its seventh year on Mars to 7.4 kilometers (4.6 miles), which is more than in any previous year. The rover's total odometry for its seventh anniversary is 26.7 kilometers (16.6 miles).

Opportunity and Spirit, which landed three weeks apart, successfully completed their three-month prime missions in April 2004, then began years of bonus extended missions. Both have made important discoveries about wet environments on ancient Mars that may have been favorable for supporting microbial life. Spirit's most recent communication was on March 22, 2010. On the possibility that Spirit may yet awaken from a low-power hibernation status, NASA engineers continue to listen for a signal from that rover.

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover project for NASA's Science Mission Directorate, Washington.